Principal end products of the steel making industry include bars, including rebar and dowel bar, and extruded tubing including pipe. Iron ore is fed into a huge blast furnace operated at a very high temperature to which is added coke or coal as a reducing agent to remove oxygen from the iron ore. The resulting molten iron is then added to scrap steel that has been heated in a separate furnace, and pure oxygen is blown into the mixture, whereby the oxygen reacts with iron and impurities in the charge to produce the heat necessary to refine the charge into steel. This molten steel may be poured through a mold, cooled and rolled into blooms, billets, and slabs, which can then be hot rolled by means of the grooved rolls of a bar mill to produce steel bars. Alternatively, the heated steel may be forced through a die to form seamless steel tubing and pipe.
Such solid bar may have grooves formed on its exterior surface to produce reinforced bar (“rebar”), which is widely used within the construction industry to reinforce poured concrete against the effects of environmental stress. Solid bar with a smooth exterior surface is called “dowel bar”, and is used for highway construction, primarily as a support piece in concrete (for example, as a component of a dowel bar basket assembly. Hollow metal tubing or pipe is used extensively within the utility industry to transmit oil, gas, and water.
Rebar set in concrete can easily corrode over time, which will reduce its effectiveness in reinforcing the concrete. Likewise, piping laid in the ground can corrode over time due to groundwater and acidic materials contained in the soil. Therefore, it is important to render such rebar and piping corrosion-resistant through the application of a protective surface coating. While steel is commonly hot-dip galvanized with molten zinc for heating ducts and storage tanks, or electroplated with chromium for the manufacture of cans and other containers, rebar and piping manufacturers have gravitated towards the use of liquid or powder coatings that may be sprayed onto the rebar or pipe as it travels at high speeds over conveyor lines within the manufacturing plant.
Flat conveyor belts have been used for a long time by the manufacturing industry to convey products between different work stations within the manufacturing process. Similarly, idle wheels can be used on gravity-type conveyors to support the products as they move along the conveyor line. However, products or boxes can easily fall off a conveyor belt or series of roller wheels, so lateral edges or guide rings are commonly applied to the edges of such conveyor lines to prevent undue lateral movement of the load during transport which could otherwise require the conveyor line to be stopped to retrieve the fallen load. See, e.g., U.S. Pat. No. 4,448,296 issued to Tabler.
The circular cross section of rebar or pipe, however, permits such products freely to roll laterally while traveling along a conveyor belt or gravity-type conveyor. Such uncontrolled lateral movement can lead to the strands of rebar or pipe becoming tangled or jammed on the conveyor line. Therefore, conveyor lines have been equipped with rollers having V-shaped or U-shaped grooves for restraining a rebar or pipe strand against lateral movement while it is transported longitudinally over the roller. See, e.g., U.S. Pat. No. 3,063,533 issued to Cook; U.S. Pat. No. 3,964,435 issued to Horn et al.; and U.S. Pat. No. 2,715,958 issued to Lindstrom et al. Such devices typically employ a motorized chain and sprocket assembly for providing the necessary propulsive force that transports the rebar or pipe longitudinally over the conveyor line.
Depending upon the manufacturing step that is being undertaken, it can be important to properly orient loads on a conveyor line so that they are evenly spaced across the width of the conveyor. For example, U.S. Pat. No. 4,166,526 issued to Wykes et al. uses first and second divider discs with guide faces to pre-separate metal bars undergoing transport prior to their passage over a magnetic roller that laterally spaces the bars with uniform spaces between each bar. Similarly, U.S. Pat. No. 3,071,236 issued to Hahn et al. employs V-belts on a conveyor line to place crackers in aligned orientation across the width of the conveyor line.
Once pipe has been laterally aligned and transported along the length of a conveyor line with V-shaped rollers, a throat plate can be employed to stop the movement of a pipe strand until the previous pipe strand has passed to avoid collisions. See U.S. Pat. No. 2,597,941 issued to Long. U.S. Pat. No. 2,169,624 issued to Weiss et al. discloses the use of idler rollers made of rubber for providing a shock resistant and non-abrasive means for transporting material over a conveyor line.
Other known pipe conveyors include mechanisms for transporting the pipe laterally from one conveyor line to another conveyor line or to a run-off table. See, e.g., U.S. Pat. No. 4,593,807 issued to Cattaneo et al.; U.S. Pat. No. 2,873,840 issued to Kerr et al.; and U.S. Pat. No. 1,021,582 issued to Daniels et al.
While such devices previously known within the industry may be capable of aligning rebar or pipe across the width of a conveyor line for evenly spaced longitudinal transport along the line until they are moved to another line or receiving station, the exterior grooves of rebar often interact with the V-shaped grooves of the conveyor line feed rollers to cause the rebar to rotate during transport. Likewise, vibration induced upon dowel bar or pipe by such V-shaped grooves can cause such dowel bar or pipe to rotate. Were such bar or pipe merely being transported by the conveyor line between work stations or during a quenching operation, this rotation would not be problematic. However, during a surface coating process or an abrasion cleaning process prior to such coating, the entire exterior surface of the rebar or pipe must be accessible to the abrasion cleaning medium and coating product, or else the rebar or pipe surface will be unevenly coated. Rotation of the rebar or pipe during transport can interfere with this continuous abrasion cleaning and coating process.
Therefore, it would be very advantageous to provide a continuous means for transporting multiple strands of rebar or pipe along a conveyor line with controlled lateral spacing between the rebar or pipe strands and without rotation so that all of their exterior surface area may be accessible during the abrasion cleaning and coating processes. Moreover, the conveyor line downstream of the coating process must be designed to prevent chipping of the protective coating from the rebar or pipe after it has been applied.